Overlay Grating Trench Design for Semiconductor Lithography Accuracy
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Solution Overview
Problem
As semiconductor feature sizes continue to decrease, the complexity of fabrication processes increases, particularly in achieving accurate overlay between layers of semiconductor devices, which is crucial for maintaining production efficiency and reducing costs.
Innovation Solution
The advanced lithography process involves forming overlay gratings and trenches in specific configurations to enhance the accuracy of optical overlay measurements, utilizing diffraction-based or image-based techniques to improve measurement results by increasing light illumination and minimizing interference from perpendicular trenches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If feature sizes continue to decrease to increase functional density, then production efficiency increases and costs decrease, but overlay accuracy between layers becomes more difficult to achieve
Solution Approach 1:
The patent replaces mechanical alignment methods with optical measurement techniques. Overlay gratings are formed on different layers and measured using optical diffraction or image-based methods, allowing precise overlay measurement without physical contact or mechanical intervention between layers
Solution Approach 2:
Overlay gratings serve as intermediary measurement structures between the actual device layers. These gratings are formed in addition to the device structures and used as reference markers for overlay measurement, enabling indirect but precise measurement of layer alignment
2Device complexity
If conventional overlay measurement methods are used with decreasing feature sizes, then measurement process remains simple, but measurement accuracy deteriorates due to interference and insufficient light illumination
Solution Approach 1:
The measurement system is segmented into distinct functional components: overlay gratings formed on specific layers, illumination sources, and detection systems. The overlay grating itself is segmented into periodic structures that diffract light at predictable angles, enabling precise measurement
Solution Approach 2:
The patent transitions from direct real-space imaging to reciprocal space (diffraction pattern) for measurement. By measuring the diffraction angles and intensities of light scattered from the overlay gratings, overlay accuracy is improved beyond what direct imaging can achieve at small feature sizes
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy of overlay measurements, thereby improving the precision of semiconductor device fabrication and addressing the challenges of smaller feature sizes, leading to more efficient and cost-effective production.
Implementation Method 1
utilizing diffraction-based or image-based techniques to improve measurement results
Implementation Method 2
The formation of the trench increases the light passing through the layer and illuminating the overlay grating under the layer
Data Source
AI summary
A method for forming a semiconductor device structure is provided. The method includes forming a first overlay grating over a substrate. The first overlay grating has a first strip portion and a second strip portion, and the first strip portion and the second strip portion are elongated in a first elongated axis and are spaced apart from each other. The method includes forming a layer over the first overlay grating. The layer has a first trench elongated in a second elongated axis, the second elongated axis is substantially perpendicular to the first elongated axis, and the first trench extends across the first strip portion and the second strip portion. The method includes forming a second overlay grating over the layer. The second overlay grating has a third strip portion and a fourth strip portion.